There are many types of heat exchangers, tailored for use in a wide variety of thermodynamic systems. One type of heat exchanger is a counter-flow heat exchanger. Counter-flow heat exchanges are sometimes used as recuperators, which may be placed downstream from a compressor, on the cold side, and downstream from a gas turbine on the hot side. The recuperator may be employed to preheat the compressed air being fed to the combustor of the gas turbine. There are many other applications for such counter-flow heat exchangers, however.
In operation of a counter-flow heat exchanger, the cold fluid flows in an opposite direction (i.e., at about a 180-degree angle) to the flow of hot fluid, in contrast to, for example, a cross-flow heat exchanger, in which the cold and hot fluids proceed at a 90-degree angle to one another. The fluids in the heat exchanger, which may be at different pressures in some thermodynamic systems, may be maintained as separate streams without mixing. Heat transfer is thus effected through a barrier, such as a plate-and-fin arrangement. In general, higher thermal transfer efficiencies can be achieved with the counter-flow heat exchangers, but the design and assembly of such devices is often more complex, and thus generally more expensive than cross-flow designs.
Further, special forming processes, and thus forming tools, are often called for in the design of the more-complex heat exchangers, complicating the process of scaling the heat exchangers for different applications. In addition, the hookup where the heat exchanger connects to the pipes of the thermodynamic system often provides a failure point for plate-and-fin designs, as the flange connection may be supported unevenly across the plates, or even by a single plate, of the plate-and-fin assembly.